Shaftless cone crusher and tilting member therefor



Feb. 9, 0, Q GRUENDER 2,310,737

SHAFTLESS GONE CRUSHER AND TILTING MEMBER THEREFOR Filed July 26, 1940 2 Sheefcs-Sheet 1 fie Wwe fw; @sm/74 7 @9am/zwei" Feb. 9, 1943. o, Q GRUENDER 2,310,737

SHAFTLESS CONE CRUSHER AND TILTING MEMBER THEREFOR Filed July 26, 1940 2 SheebS--Shee-t 2 Planted Feb. s, 194s smirmss come causaran AND mma Mamas. manson Oscar C. Gruendcr, Milwaukee, Wil., assigner to Nordberg Manuf Company, Milwaukee,

actnring Wis., a corporation of Wisconsin Application July 26, 1949, Serial No. 347,693 16 Claims. v(Cl. 83-10) My invention relates to an improvement in gyratory crushers and has for one purpose the provision oi' a ygyratory crusher in which the crusher head is gyrated without the employment of a crushing shaft unitary with the head.

Another purpose is the provision of a head and an actuating structure therefor in which any risk of breakage of the head itself is reduced to a minimum.

Another purpose is the provision of improved means for actuating or gyrating a gyratory crusher head.

Another purpose is the provision of improved means for supporting 'a gyrated crusher head.

Another purpose is the provision of improved oil sealing means for gyratory crushers.

Another purpose is the provision of a simplified and improved method for producing a satisfactory gyrating movement of a gyratory crusher head.

Other purposes will appear from time to time in the course of the specification and claims.

I illustrate my yinvention more or less diagrammatically in the accompanying drawings wherein:

Fig. 1 is a vertical axial section;

Fig. 2 is a similar partial section on an enlarged scale; and

Fig. 3 is a detail.

Like parts are indicated by like symbols throughout the specification and drawings.

Referring to the drawings, I illustrate any suitable base or foundation I, which may be of concrete or the like and which has a central opening 2 aligned with the crusher below described.

3 indicates a circumferential and generally cylindrical main frame which is shown as terminating at its upper end in an outwardly projecting flange 4, having opposite beveled converging faces 5, 6 and a generally horizontal top face l. A plurality of access apertures 3 are provided in the lower portion of the frame, which may be closed by any suitable plates or closures 9. I indicates any suitable radial elements which extend inwardly from the circumferential main frame 3 to a central sleeve structure II. The central sleeveV isoutwardly expanded as at I2 and is provided with an aperture as at I3, which receives the inner end I4 of the shaft housing I5. I6 is another enlargement of the shaft housing I5, which penetrates and closes an aperture in the end of an outwardly extending sleeve or enlargement Il, herein shown as formed integrally with the circumferential main frame 3. |3 is an outer bearing sleeve forming a portion of the shaft housihg I5.

Mounted upon the upper edge enlargement I2 of the central sleeve I I is a supporting structure including an outer member I9 and an inner member 20, the latter being generally aligned with the lower portion of the sleeve I I and being connected with the member I9 by a horizontal portion 2|. 'Ihis structure may be bolted to the sleeve portion I2 as by any suitable bolts 22. The member I9 has an upwardly and outwardly extending portion 23 which carries a spherical bearing plate or Lring 24 defining a sphere, the center of which is indicated at X in Fig. 1.

Resting upon the flange 4 of the main frame is a bowl supportingring 30 having an inner generally cylindrical portion 3|, inwardly screw threaded as at 32. The member 30 has a circumferential channel 33 having faces 5 and 6 engaging the flange 4. Relative rotation of the parts is prevented by any suitable pins 34, having an enlargement 35 positioned between the members 4 and 30. Upward movement of the member 30 is normally prevented by the employment of coil springs 36, which may be nested in and between upper spring abutment members 31 and lower spring abutment members 33. 39 indicate tension members or bolts extending downwardly through the member 3|), the upper spring abutments 31 and the lower spring abutments 38. The compression of the springs may be adjusted by varying the location of the nuts 40 at the lower ends of the tension members 39. It will be observed that the upper spring abutments 31 penetrate beneath the flange 4.

Adjustable in the screw threaded portion 3| of the bowl support 30 is a bowl structure including the outer generally cylindrical wall 45, screw threaded as at 46, in mesh with the screw threaded portion 3| of the bowl support 30. Any suitable means not herein shown may be employed wilth the bowl structure for imparting to it a vetrical adjustment. In order to prevent the penetration of dust to the threads 32, 46. I may provide any suitable sealing ring, shown for example in Fig. 3. I illustrate for example a U-shaped ring 40a, which may be secured as by screws 40h to the lower portion ofthe bowl structure 3|, and which receives in its U-shaped aperture any suitable wiping ring 40e of felt or the 1ike. The bowl structure includes a lowerfor the upper wall 4I, and any suitable bowl liner 50 may be employed as a wear-taking crushing element, as shown, having outwardly extending hook-shaped lugs 5I which may be received by the U-shaped locking bolts l2, located in the space between the walls 45, 41 and 4l. Since the looking means and the access thereto do not of themselves form Dart of the present invention, they will not be further described.

53 is any suitable generally cylindrical apron shown as resting upon the top of the bowl. 54 is any suitable forward spout mounted on a structure Il adjustable on the screw threaded portions of rods It, which may be suitably mounted upon the crusher.

51 indicates the head or top of a tilting member or actuator shaped like a, spherical segment,which has a bottom plane surface I8 and a top spherical surface BI. The plane surface rests on a plane bearing plate or ring III, herein shown as resting on the portion 2| and having formed integrally with it a cylindrical sleeve Il located within the member 24. A lower bearing sleeve l2 coaxial with the sleeve 8| is located within the member I I. The two sleeves are concentric but are shown with slightly dierent diameters. They receive a rotating sleeve 63 having a central gear I4 projecting outwardly into the space within the enlargement I2 and located intermediate the bearing sleeves 6| and 82. The gear C4 is also provided with a counterweight Il upwardly extending into the space between the members II and 20, which may be filled with lead or the like.

41 is a pinion in mesh with the gear I4 and mounted on the drive shaft Il, driven by any suitable pulley 'I'he drive shaft is rotatably mounted in bearing sleeves 1l, 1I within the portions I l and I 8. as shown in Fig. 1. I'he sleeve Il is eccentrically apertured as at 12 to receive a downwardly extending hollow stem 1I, herein shown as integral with' the top or head l1 of the tilting member. 'I4 indicates any suitable bearing sleeve located within the eccentric aperture of the sleeve 4I. It is to be understood that rotation of the drive shaft Il rotates the sleeve l2 and imparts an eccentric movement to the stem 12 and the head 51. The axis of the stem is parallel with the axis of rotation of the sleeve 43, and the result is a movement along a horizontal plane, the head l1 resting upon and sliding upon the ilat bearing plate 40. Observe that the bottom nat surface il of the head is upwardly re-curved adjacent its Junction with the hollow stem 12, as at Il, and that the wall of the central aperture of the stem is outwardly curved as at li and re-curved as at 82, indicated in Fig. 2, dening a space of substantial content from the top of the head and providing a structure of great strength and with an economy of material. The top of the head may be closed as by any suitable plate 44, and the bottom may be similarly closed as by a plate I4, the two plates being connected by a lubricating tube I6 open at top and bottom. a indicates any suitable oil aperture adapted to deliver oil to the bearings and 1I.

Resting upon the upper spherical surface of the head 51 is a crusher head generally indicated as il. It is provided with a bearing plate Il having a lower concave surface conforming to the sph'erical convex surface 59 of the tilting member l1. It is to be understood, of course, that it is a matter of choice as to whether the bearing 9| is mounted upon the head or the tilting member, but I ilnd it convenient to mount it on the head, as shown in Figs. 1 and 2, for example by a key or wedge lia.

The lower portion of the head is provided with a. spherical surface l2 adapted to be engaged and to be received by the bearing 24 on the member 23. '$3 indicates a crushing mantle which may 5 be thrust down upon the outer conic surface I4 of the head as for example by a thrust member or sleeve ll, which in turn is engaged by a split nut 98 screw threaded as at I1 in relation to a holding sleeve 98, which has an enlarged head 9! located 10 within an aperture of corresponding size within the head. III is any suitable lug penetrating a slot III, whereby relative rotation of the sleeve Il and the head l0 is prevented. The split nut l1 is held together for example lby bolts 21a and is provided with an upwardly and outwardly extending portion Il2, upon which any suitable feed limiting or feed distributing plate Ill may be mounted, and may be held 'in position for example by bolts II4. It will be understood that the above described structure is self-tightening in that the eil'ect of the contact with the crushing material in the crushing cavity defined between the members 50 and I3 is to tighten the split nut and also to direct a lateral thrust in response to. the peening of the manganese steel, of which the mantle Il is formed. When it is desired to release the mantle, however, it is easy to remove the bolts lla and separate the split nut and thus free the mantle l2 from the securing sleeve Il. I find it useful to provide a wear-taking ring ill below the lower edge of the mantle Il to protect a downwardly and outwardly extending lower end I of the head. Secured to this lower head i",

as by bolts or screws Ill, is an apron ill having an inwardly extending portion I4! which defines a space Il., which may receive dust or dirt and serve as a retainer until such dirt may be removed by any suitable plugs or closures III.

Mounted on an inner portion of the apron III, Ill is a spherical surfaced bearing ring Il! concentric with the opposed spherical surface of the member Ill. 'I'he ring IIS is formed continuously with a generally cylindrical ring I I4 slidable along the outer face of the member IQ, which is provided with sealing piston rings lli. III is a lug downwardly extending from the ring H4, which is positioned in the recess II1 to prevent rotation of the ring H4 about the frame. The structure III, |I4 rests gravitally upon the bearing ring H2 but, to obtain an increased sealing eifect, I also spring load it by employing springs III, the upper ends of which are compressed against the portion 22a of the outwardly extending portion 22 of the member Il. and the lower ends of which are compressed against the bottom of the ring H4. Any suitable housing or guide llneans for the springs may be employed, as at In order to return the oil which passes over the outer edge of the bearing 24, I provide a deilector ring I2! which defines a space or small sump I2I, .connected by passages |22, with a sump or space |22 above the-member 23 and exterior of the bearing plate Il, as shown in Fig. 2;,thence oil may pass by the passage or passages I 24 to the interior of the enlargement i2 of the central main frame portion Il. When lubricating. the device, oil may be supplied from any suitable pump not shown, along an oil supply line III, to the bottom cap Ill of the sleeve structure I i. It passes thence upwardly through the supporting means |22 for the eccentrically apertured sleeves 42, the details of which supporting means are not shown as they do not form 75 part of the present invention. Oil passes up- .wardly through the space 12 and through the central oil passage ofthe tiltingdevice: It

then lubricates the bearing surfaces of the members Il and Il, which may, if desired, be provided with distributing ducts not herein shown. The oil thence reaches the sump |23 and returns to the space within the enlargement I2 and reaches the oil outlet passage Ill and thus re- ,Y

turns to the pump by-the line |38. Oil also travels along the shaft I8 and reaches the sealing means, which include the housing |31, from' which extends another oil return line |88, which communicates -with the main oil return line |38.

Itv will be realized that, whereas I have described and shown a practical and operative device, nevertheless many changes may be made in the size, shape, number and disposition of parts without departing from the spirit of my invention. I therefore wish my description and drawings to be taken as in a broad sense illustrative or diagrammatic, rather than as limiting me to my precise showing.

'I'he use and operation of my invention are as follows:

I illustrate herein a crusher in which a generally conic crusher head 90 is gyrated within a normally fixed crushing Abowl 50, the bowl overhanging the head, and the opposed mantle 93 the bowl liner 80 having generally conical surfaces which deflne a crushing cavity. It has been past practice to employ a crushing head of this general type in which an integral downwardly extending shaft is seated within eccentric aper' tures of a rotated sleeve. Breakage of both head and shaft is not infrequent and causes expense of replacement and delays for replacement and repair which reduce the emciency of the machine. In addition. in the earlier machine, the

bore within the eccentric had its center line at an angle, with the center line of the outer diameter of the eccentric. It will be noticed that in the structure of the present application the center line of the eccentric is parallel with the center line of the crusher.

In my invention I provide a crushing head and means for supporting and actuating it, which eliminates the breakable downwardly extending shaft, and in which the crushing thrust against the head is directly against a supporting means, so that any tendency of any part of the head to break under crushing stress is greatly reduced.

Referring for example to Fig. l, in the operation of the device the rotation of the shaft 68 ro tates the eccentrically apertured shaft 63 about a preferably vertical axis. The shaft 88 is provided with an eccentric aperture which also has preferably a vertical axis. In this aperture is received a downwardly extending shaft 13, which is shown as integral `with or rigidly secured to the tilting member l. The tilting member has a flat lower surface 58 which operates in a horizontal plane on the bearing plate 60. It has a spherical upper surface 59 described about the center A of Figs. 1 and 2, which engages a conforming spherical surface of the bearing member 9| of the head 90. An outer spherical bearing 24v, concaved oppositely to the bearing for the element 2| and contacting a cooperative spher-k ical bearing on the head 90, aids in guiding the head, particularly at no-loads. with the result that the eccentric movement of the tilting member 51, in response to rotation of the drive shaft 6B, produces a gyratory wobble of the head 90. The spherical bearing 24 is described about the center X of Fig. 1. In effect, there is a point of close ap oach of the head Il toward the bowl, which asses circumferentially around the crushing ca ty as the head l1 `is turned eccentrically. g

Thecrushing thrust in the cavity, defined by the members Il and Il, is received first by thr head and then by the tilting member Il, and is transmitted to the central portion of the main frame alongthe bearing sleeve 80, and also along the bearing sleeve 24. There is no` overhanging of the free unsupported part of the head which is subjected to crushing stress. Nor is there any depending shaft which is subjected to bending moment. v

'I'he machine is easily disassembled for repair or replacement. The whole structure can be readily upwardly removed. Thereafter, by releasing the bolts 91a, the split sleeve 93 is released and the mantle 93 and the pressure sleeve 95 may be upwardly lifted from the head. A readily removable securing means is important with the 4remove them. However, once the screws 91a are released, and they can be, for example, burned oil with a blowtorch, the split sleeve 96 can be easily opened and the entire device disassembled.

It will be observed that the bowl, including the bowl liner 50. is normally fixed and has no motion except when the presence of an uncrushable mass of material in the crushing cavity causes the bowl to rise against the thrust of the spring 36, in response to the movement of the head toward the bowl in the course of the crushing nip. The head is a part of the gyratory movement about the center X," as shown in Fig. 1. The material passes through the crushing cavity under gravity. In order to permit this gravital feed. it is necessary that the angleof the head approximate the angle of repose of the material being crushed. It may, for example, have an angle of the order of forty degrees from the horizontal, but the angle may vary in different machines and in different sizes of machines. It is essential. however, that the angle be sufficiently high to prevent particles from resting upon the head and to insure that they move gravitally downwardly through the crushing cavity at all times, unless they are actually gripped between the opposed crushing members.

I claim:

l. For use in a gyratory crusher having a normally xed bowl, a crushing head including a generally conic body portion having a crushing face of an angle higher than the angle of repose outer edge thereof, the center of said surface being located above the top of the crushing portion of the head, and a normally fixed support for said head including an upwardly concave spherical bearing element adapted to receive and .4 'conform to saiddownwardly convex spherical beaxingsurfaceofthecnishinghead. l

2. Foruseinagyratorycrusherhavinganormaliy fixed bowl, a generally conic truncated crushing head, the conic face of whichis of an 'inclination higher than tbe angle of repose of material fed theretma cavity extending upwardly intothebottomofsaidhead,saidcavitybeing plate mounted on the top of said stem.

3. For use in a gyratory crusher having a normally fixed bowl, a generally conic truncated crushingheadtheconicfaceofwhichisofan inclination higher than the angle of repose of material fed thereto, a cavity extending upwardly into the bottom of said head, said cavity being defined by a generally spherical surface. an axial aperture in said head, a stem extending upwardly through said aperture a substantial distance above the top of the head, and an enlargement at the lower end of said stem, the bottom of said head being recessed to receive said enlargement. a conic mantle mounted upon the exterior surface of the head, a thrust member upon said stem,

adaptedtobeopposedtotheupperedgeofsaid.

mantle, compression means on said stem adapted to urge said thrust member against the upper edge of the mantle, and a laterally extending feed plate mounted'on the top of said stem. and means for preventing relative rotation of stem and head.

4. For use in a gyratory crusher having a normally xed bowl, a generally conic truncated crushing head, the conic face of which is of an inclination higher than the angle of repose lof material fed thereto, a cavity extending upwardly into the bottom of said head. said cavity being defined by a generally spherical surface, an axial aperture in said head, a stem extending upwardly through said aperture a substantial distance above the top of the head, and an enlargement at the lower end of said stem, the bottom of said head being recessed to receive said enlargement, a conic mantle mounted upon the exterior surface of the head, a thrust member upon said stem, adaptedtobeopposedto the upper edge of said mantle, compression means on said stem adapted to urge said thrust member against the upper edge of the mantle, and a laterally extending feed plate moimted on the top of said stem. said head having adjacent its bottom a downwardly convex spheril bearing surface surrounding said cavity, the center of said surface being located adjacent the top of the head.

5. For use in a gyratory crusher having a ncrmally nxed bowl. a generally conic crushing head having a conic upper and outer surface of an inl clination higher than the angle of repose of the material fed thereto, said head having a cavity extending upwardly into the bottom of the head and a bearing liner tlxed'in said cavity, said linerl having a generally spherical downwardly concave annular bearing surface, said crushing head being truncated and having a stem removably securedtheretoandextendingupwardlythrough ofsaidtnmcatedportiomamantle ontheexterior conic surface ofthe head,andmeansassociatedwithsaidstemfor thrusting said mantle downwardly against said 8. Ibi', in

surface of the mantle.

7. For use in a gyratory crusher having a normally xed bowl, a generally conic crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material fed thereto, said head having a cavity extending upwardly and inwardly into the bottom of the head and having a generally annular spherical downwardly concave bearing surface thereabout, said head having an axial aperture extending upwardly therethrough, a stem extending upwardly through said aperture and having an enlarged lower portion intertting with an enlarged lower portion of said aperture, a mantle mounted on the exterior conic surface of the head, and means associated with said stem for thrustingv the mantle downwardly against said head and for thereby holding the mantle normally fixed in position.

8. For use in a gyratory crusher having a normally fixed bowl, a generally conic crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material fed thereto, said head having a cavity extending upwardly and inwardly into the bottom of the head and having a generally annular spherical downwardly concave bearing surface thereabout, said head having an axial aperture extending upwardly therethrough, a stem extending upwardly through' said aperture and having an enlarged lower portion interfitting with an enlarged lower portion of said aperture,v a mantle mounted on the exterior conic surface of the head, and means associated with said stem for thrusting the mantle downwardly against said head and for thereby holding the mantle normally ilxed in position, the stem being removable downwardly through said aperture.

9. For use in a gyratory crusher having a normalty fixed bowl, a generally conic crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material fed thereto, said head having a. cavity exending upwardly and inwardly into the bottom of the head and having a generally annular spherical downwardly concave bearing surface thereabout, said head having an axial aperture extending upwardly therethrough, a stem extending upwardly through said aperture and having an enlarged lower portion interfltting with an enlarged lower portion of said aperture.

a gyratory crusher having a nora mantle mounted on the exterior conic surface of the head, and means associated with said stem for thrusting the mantle downwardly against said head and for thereby holding the mantle normally ilxed in position, and means for normally preventing relative rotation of head and mantle.

y10. For use in a gyratory crusher having a normally fixed bowl, a generally conic truncated crushing head having a. conic upper and outer surface of an'inclination higher than the angle of repose of the material fed thereto, said head having a coaxial central spherical bearing cavity extending upwardly into the bottom of the head and of a maximum diameter greater than that of the truncated part of the head, the center of sphericity of said cavity being located substantially below said head, said head having a downwardly convex spherical .'bearing surface about a lower portion thereof surrounding said first cavity, the center of sphericity of said downwardly convex bearing surface being located above the top of the crushing cavity deilned by said head, said head having a stem removably secured thereto and extending upwardly from the center of the truncated portion.

11. For use in a gyratory crusher having a normally fixed bowl, a generally conic truncated crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material fed thereto, said head having a coaxial central spherical bearing cavity extending upwardly into the bottom of the head and of a maximum diameter greater than that of the truncated part of the head, the center of sphericity of said cavity being located substantially below said head, said head having a downwardly convex spherical bearing surface about a lower portion thereof surrounding said first cavity, the center of sphericity of said downwardly convex bearing surface being located above the top of the crushing cavity deilned by said head, said head having a stem removably secured thereto and extending upwardly from the center of the truncated portion, the lower end of said stem extending into said head and terminating adjacent the top of said bearing cavity.

12. For use in a gyratory crusher having a normally fixed bowl, a generally conic truncated crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material fed thereto, said head having a coaxial central spherical bearing cavity extending upwardly into the bottom of the head and of a maximum diameter greater than that of the truncated part of the head, the center of sphericity of said cavity being located substantially below said head, said head having a downwardly convex spherical bearing surface about a lower portion thereof surrounding said rst cavity, the center of sphericity of said downwardly convex bearing surface being located above the top of the crushing cavity defined by said head, said head having a stem removably secured thereto and extending upwardly from the center of the truncated portion, and a sealing apron extending downwardly from a lower portion of said head, said sealingapron having an upwardly concave spherical bearing surface concentric with the downwardly convex bearing surface about the lower portion of the head, and of greater radius.

13. For use in a gyratory crusher having a normally fixed bowl? a generally conic truncated crushing head having a conic upper angouter surface of an inclination highertlwtli angle.V

tially below said head, said head having a downwardly convex spherical bearing surface about a lower portion thereof surrounding said first cavity, the center of sphericity of said downwardly convex bearing surface being located above the top of the crushing cavity defined by said head, said head having a stem removably secured thereto and extending upwardly from the center of the truncated portion, and a sealing apron extending downwardly from a lower portion of said head, said sealing apron having an upwardly concave spherical bearing surface concentric with the downwardly convex bearing surface about the lower portion of the head, and of greater radius, and having a sump located at a level below said upwardly concave surface.

14. For use in a gyratory crusher having a normally fixed bowl, a crushing head including a generally conic body portion having a crushing face of an angle higher than the angle of re'pose of the material delivered thereto, said body portion being penetrated upwardly from below by an aperture of substantial depth in relation to its transverse diameter, said aperture being defined by a downwardly concave generally spherical surface, and actuating means for said head including a tilting member and means for gyrating it, said tilting member having a tilting head with an upwardly convex spherical surface conforming to the spherical surface in the bottom of the head, said head having a downwardly convex spherical bearing surface adjacent the lower outer edge thereof, the center of said surface being located above the top of the crushing portion of the head, and a. normally fixed support for said head including an upwardly concave spherical bearing element adapted to receive and conform to said downwardly convex spherical bearing surface of the crushing head, said head having a sealing apron extending downwardly from a lower portion thereof, said sealing aprong having an upwardly concave spherical bearing surface concentric with said downwardly convex spherical:

bearing surface but of greater radius, and an opposed, conforming, downwardly convex wiping member movably mounted in relation to said fixed support.

15. For use in a gyratory crusher having a normally xed bowl, a crushing head including a generally conic body portion having a crushing face of an angle higher than the angle of repose of the material delivered thereto, said body portion being penetrated upwardly from below by an aperture of substantial depth in relation to its transverse diameter, said aperture being defined by a downwardly concave generally spherical surface, and actuating means for said head including a tilting member and means for gyrating it. said tilting member having a tilting head with an upwardly convex spherical surface conforming to the spherical surface in the bottom of the head, said head having a downwardly convex spherical bearing surface adjacent the lower outer edge thereof, the center of said surface being located above the top of the crushing portion of the head, anda normally xed support for said head including an upwardly concave spherical bearing element Yadapted to receive and conform to said downwardly convex spherical bearing sur- Y face of the crushing head. said head having a sealing apron extending downwardly from a lower portion thereof, said sealing apron having an upwardly concave spherical bearing surface concentric with said downwardly convex spherical bearing surface but of greater radius. and an opposed, conforming, downwardly convex wiping member movaby mounted in relation to said xed support, said sealing apron having a sump located at a level below said upwardly concave bearing surface.

16. For use in a gyratory crusher having a normally fixed bowl. a generally conic truncated crushing head having a conic upper and outer surface of an inclination higher than the angle of repose of the material ted thereto, said head having a coaxial central spherical bearing cavity extending upwardly into the bottom of the head and of a maximum diameter greater than that of the truncated part of the head, the center of sphericity of said cavity being located substantiaily below said head, said head having a downwardly convex spherical bearing surface about a lower portion thereof surrounding said nrst cavity, the center of sphericity of said downwardly convex bearing surface being located above the top of the crushing cavity defined by said head, saidheadhaving astemsecuredtheretoandextending upwardly from the center of the truncated portion.

.. OSCAR C. GRUINDER. 

